More insight into mesenchymal stem cells and their effects inside the body

Modulatory effects of mesenchymal stem cells on microglia in ischemic stroke

Ischemic stroke accounts for 70-80% of all stroke cases. Immunity plays an important role in the pathophysiology of ischemic stroke. Microglia are the first line of defense in the central nervous system. Microglial functions are largely dependent on their pro-inflammatory (M1-like) or anti-inflammatory (M2-like) phenotype. Modulating neuroinflammation via targeting microglia polarization toward anti-inflammatory phenotype might be a novel treatment for ischemic stroke. Mesenchymal stem cells (MSC) and MSC-derived extracellular vesicles (MSC-EVs) have been demonstrated to modulate microglia activation and phenotype polarization. In this review, we summarize the physiological characteristics and functions of microglia in the healthy brain, the activation and polarization of microglia in stroke brain, the effects of MSC/MSC-EVs on the activation of MSC in vitro and in vivo, and possible underlying mechanisms, providing evidence for a possible novel therapeutics for the treatment of ischemic stroke.

Characterization and bioassays of extracellular vesicles extracted by tangential flow filtration

Aim: To evaluate the efficiency of tangential flow filtration (TFF) in improving the yield of human umbilical cord mesenchymal stem cell (MSC)-derived extracellular vesicles (hucMSC-EVs) while promoting cell regeneration under oxidative stress. Methods: HucMSC-EVs were extracted from supernatants by ultracentrifugation (UC-EVs) and TFF (TFF-EVs), followed by feature characterization and bioactivity assays. Results: The yield of TFF-EVs increased 18-times compared with that of UC-EVs. TFF-EVs displayed proliferation-promoting ability similar to that of UC-EVs in the damaged HaCaT cell model with ultraviolet radiation B (UVB) and H₂O₂. Furthermore, the antiapoptotic effects of TFF-EVs were improved, whereby the apoptosis rate exhibited a 3.7-fold decrease. Conclusion: HucMSC-EVs extracted by TFF show a higher yield and rejuvenate the damaged HaCaT cells induced by oxidative stress.

An update on stem cells applications in burn wound healing

Burn wounds have proven to be capable of having a long lasting devastating effects on human body. Conventional therapeutic approaches are not up to the mark as they are unable to completely heal the burn wound easily and effectively. Major pitfalls of these treatments include hypertrophic scarring, contracture and necrosis. Presence of these limitations in the current therapies necessitate the search for a better and more efficient cure. Regenerative potency of stem cells in burn wound healing outweigh the traditional treatment procedures. The use of multiple kinds of stem cells are gaining interest due to their enhanced healing efficiency. Distinctions of stem cells include better and faster burn wound healing, decreased inflammation levels, less scar progression and fibrosis on site. In this review, we have discussed the wound-healing process, present methods used for stem cells administration, methods of enhancing stem cells potency and human studies. Pre-clinical and the clinical studies focused on the treatment of thermal and radiation burns using stem cells from 2003 till the present time have been enlisted. Studies shows that the use of stem cells on burn wounds, whether alone or by the help of a scaffold significantly improves healing. Homing of the stem cells at the wound site results in the re-epithelialization, angiogenesis, granulation, inhibition of apoptosis, and regeneration of skin appendages together with reduced infection rate in the human studies. Several studies on animals have shown that stem cells can effectively promote wound healing. Although more research is needed to find out the effectiveness of this treatment in patients with severe burn wounds.

Cold Atmospheric Pressure Plasma in Wound Healing and Cancer Treatment

Plasma medicine is gaining increasing attention and is moving from basic research into clinical practice. While areas of application are diverse, much research has been conducted assessing the use of cold atmospheric pressure plasma (CAP) in wound healing and cancer treatment—two applications with entirely different goals. In wound healing, a tissue-stimulating effect is intended, whereas cancer therapy aims at killing malignant cells. In this review, we provide an overview of the latest clinical and some preclinical research on the efficacy of CAP in wound healing and cancer therapy. Furthermore, we discuss the current understanding of molecular signaling mechanisms triggered by CAP that grant CAP its antiseptic and tissue regenerating or anti-proliferative and cell death-inducing properties. For the efficacy of CAP in wound healing, already substantial evidence from clinical studies is available, while evidence for therapeutic effects of CAP in oncology is mainly from in vitro and in vivo animal studies. Efforts to elucidate the mode of action of CAP suggest that different components, such as ultraviolet (UV) radiation, electromagnetic fields, and reactive species, may act synergistically, with reactive species being regarded as the major effector by modulating complex and concentration-dependent redox signaling pathways.

Why Should Growth Hormone (GH) Be Considered a Promising Therapeutic Agent for Arteriogenesis? Insights from the GHAS Trial

Despite the important role that the growth hormone (GH)/IGF-I axis plays in vascular homeostasis, these kind of growth factors barely appear in articles addressing the neovascularization process. Currently, the vascular endothelium is considered as an authentic gland of internal secretion due to the wide variety of released factors and functions with local effects, including the paracrine/autocrine production of GH or IGF-I, for which the endothelium has specific receptors. In this comprehensive review, the evidence involving these proangiogenic hormones in arteriogenesis dealing with the arterial occlusion and making of them a potential therapy is described. All the elements that trigger the local and systemic production of GH/IGF-I, as well as their possible roles both in physiological and pathological conditions are analyzed. All of the evidence is combined with important data from the GHAS trial, in which GH or a placebo were administrated to patients suffering from critical limb ischemia with no option for revascularization. We postulate that GH, alone or in combination, should be considered as a promising therapeutic agent for helping in the approach of ischemic disease.

The Role of Growth Hormone in Mesenchymal Stem Cell Commitment

Growth hormone (GH) is best known for its prominent role in promoting prepubertal growth and in regulating body composition and metabolism during adulthood. In recent years, the possible role of GH in the modulation of mesenchymal stem cell (MSC) commitment has gained interest. MSCs, characterized by active self-renewal and differentiation potential, express GH receptors. In MSCs derived from different adult tissues, GH induces an inhibition of adipogenic differentiation and favors MSC differentiation towards osteogenesis. This activity of GH indicates that regulation of body composition by GH has already started in the tissue progenitor cells. These findings have fostered research on possible uses of MSCs treated with GH in those pathologies, where a lack of or delays in bone repair occur. After an overview of GH activities, this review will focus on the research that has characterized GH’s effects on MSCs and on preliminary studies on the possible application of GH in bone regenerative medicine.

The role of neurogenesis in neurorepair after ischemic stroke

Stroke consists of an abrupt reduction of cerebral blood flow resulting in hypoxia that triggers an excitotoxicity, oxidative stress, and neuroinflammation. After the ischemic process, neural precursor cells present in the subventricular zone of the lateral ventricle and subgranular zone of the dentate gyrus proliferate and migrate towards the lesion, contributing to the brain repair. The neurogenesis is induced by signal transduction pathways, growth factors, attractive factors for neuroblasts, transcription factors, pro and anti-inflammatory mediators and specific neurotransmissions. However, this endogenous neurogenesis occurs slowly and does not allow a complete restoration of brain function. Despite that, understanding the mechanisms of neurogenesis could improve the therapeutic strategies for brain repair. This review presents the current knowledge about brain repair process after stroke and the perspectives regarding the development of promising therapies that aim to improve neurogenesis and its potential to form new neural networks.

Stem cell-based cell therapy for neuroprotection in stroke: A review

Neurological disorders, such as stroke, are triggered by a loss of neurons and glial cells. Ischemic stroke remains a substantial problem for industrialized countries. Over the previous few decades our understanding about the pathophysiology of stroke has enhanced, nevertheless, more awareness is required to advance the field of stroke recovery. Existing therapies are incapable to adequately relief the disease outcome and are not appropriate to all patients. Meanwhile, the majority of patients continue to show neurological deficits even subsequent effective thrombolysis, recuperative therapies are immediately required that stimulate brain remodeling and repair once stroke damage has happened. Cell therapy is emergent as a hopeful new modality for increasing neurological recovery in ischemic stroke. Numerous types of stem cells from various sources have been identified and their possibility and efficiency for the treatment of stroke have been investigated. Stem cell therapy in patients with stroke using adult stem cells have been first practiced in clinical trials since 15 years ago. Even though stem cells have revealed a hopeful role in ischemic stroke in investigational studies besides early clinical pilot studies, cellular therapy in human is still at a primary stage. In this review, we summarize the types of stem cells, various delivery routes, and clinical application of stem cell-based therapy for stroke treatment.

Stem Cell Therapy in Cerebrovascular Disease

PURPOSE OF REVIEW

The purpose of this article is to provide a review of state-of-the-art cellular therapy in cerebrovascular diseases by discussing published and ongoing clinical trials.

RECENT FINDINGS

In spite of the challenge in translating the success of cellular therapy in acute strokes from preclinical models to clinical trials, early phase clinical trial have recently shown promise in overcoming these challenges. Various stem cell types and doses are being studied, different routes of administration are under investigation, as well as defining the optimal time window to intervene. In addition, experimental methods to enhance cellular therapy, such as ischemic preconditioning, are evolving. After the failure of neuroprotectants in cerebrovascular diseases, researchers have been keen to provide a way of replacement of damaged brain tissue and to promote recovery in order to achieve better outcomes. The field has progressed from intravenous delivery in the 24- to 36-h time window to later intracerebral administration in chronic stroke in clinical trials. New optimism in acute stroke care fostered by the success of mechanical thrombectomy will hopefully extend into cell therapy to promote recovery.

Standardization and quality assessment for clinical grade mesenchymal stem cells from human adipose tissue

Background

Mesenchymal stem cells have immense potential in stem cell-based therapies, however there is a pre-requisite to develop a curative cell dose. Adipose tissue-derived mesenchymal stem cells are promising mainly due to their potential abundance, immunomodulatory effect and remarkable differentiation potential. Nevertheless, senescence may develop during their in vitro expansion due to the incidence of genetic instability. Hence, it is important to attain an ideal balance between mesenchymal stem cell growth, quality and genetic integrity before their clinical use.

Methods

Stromal vascular fraction was obtained from omentum tissue of patients undergoing liposuction procedures for morbid obesity. This study standardized a closed system protocol which can be utilized for clinical grade stem cell derivation. Stages of cell growth and characterization of human adipose tissue-derived mesenchymal stem cells were also assessed along with the chromosomal stability in these in vitro cultures.

Results

Human adipose tissue-derived mesenchymal stem cells maintained their spindle-shaped morphology and were able to proliferate and renew, confirming their suitability for in vitro cultivation and generate clinical grade mesenchymal stem cells. Immunophenotyping indicates that the cells expressed cluster of differentiation (CD)73/CD90/CD105, mesenchymal stem-cell markers, while lacked CD34/CD45/ Human Leukocyte antigen-antigen D related (HLA-DR) expression (hematopoietic cell markers). A cell cycle study demonstrated growth kinetics under in vitro culture conditions. Human adipose tissue derived mesenchymal stem cells expressed normal cell karyotype by chromosomal G-banding indicating their genetic stability at Passage 5. Mesenchymal stem cells also demonstrated trilineage differentiation.

Conclusions

Availability of adipose tissue in abundance is a major advantage for clinical applications. Furthermore, detailed characterization of human adipose tissue-derived mesenchymal stem cells, their genomic stability and differentiation potential from stromal vascular fraction of human adipose tissue would help assist in tissue regeneration and repair.

In vitro cell behaviors of bone mesenchymal stem cells derived from normal and postmenopausal osteoporotic rats

Postmenopausal osteoporosis (PMO) increases bone fragility and the risk of fractures, and impairs the healing procedure of bone defects in aged women. The stromal cell-derived factor-1α (SDF-1α)/CXC chemokine receptor type 4 (CXCR4) axis helps to maintain the biological and physiological functions of bone marrow mesenchymal stem cells (BMSCs) and increase the homing efficiency of BMSCs. The present study aimed to provide insights into the possible association between migration and osteogenic ability and the SDF-1α/CXCR4 axis in BMSCs derived from a rat model of PMO. In order to do this, the general and SDF-1α/CXCR4-associated biological characteristics as well as associated molecular mechanisms in BMSCs isolated from a PMO rat model (OVX-BMSCs) and normal rats (Sham-BMSCs) were investigated and compared. In comparison with Sham-BMSCs, OVX-BMSCs exhibited an impaired osteogenic ability, but a stronger adipogenic activity as well as a higher proliferative ability. In addition, OVX-BMSCs presented a lower chemotactic activity towards SDF-1α, lower expression levels of CXCR4 and reduced levels of phosphorylated AKT (p-AKT). Therefore, the lower expression levels of CXCR4 and p-AKT may be responsible for the impaired osteogenic ability and lower chemotactic activity towards SDF-1α of OVX-BMSCs.

Stem cell therapies for ischemic stroke: current animal models, clinical trials and biomaterials

We report the facilitation of stem cell therapy in stroke by tissue engineering and applications of biomaterials.

miR-195 in human primary mesenchymal stromal/stem cells regulates proliferation, osteogenesis and paracrine effect on angiogenesis

Mesenchymal Stromal/Stem Cells (MSC) are currently being explored in diverse clinical applications, including regenerative therapies. Their contribution to regeneration of bone fractures is dependent on their capacity to proliferate, undergo osteogenesis and induce angiogenesis. This study aimed to uncover microRNAs capable of concomitantly regulate these mechanisms. Following microRNA array results, we identified miR-195 and miR-497 as downregulated in human primary MSC under osteogenic differentiation. Overexpression of miR-195 or miR-497 in human primary MSC leads to a decrease in osteogenic differentiation and proliferation rate. Conversely, inhibition of miR-195 increased alkaline phosphatase expression and activity and cells proliferation. Then, miR-195 was used to study MSC capacity to recruit blood vessels in vivo. We provide evidence that the paracrine effect of MSC on angiogenesis is diminishedwhen cells over-express miR-195. VEGF may partially mediate this effect, as its expression and secreted protein levels are reduced by miR-195, while increased by anti-miR-195, in human MSC. Luciferase reporter assays revealed a direct interaction between miR-195 and VEGF 3′-UTR in bone cancer cells. In conclusion, our results suggest that miR-195 regulates important mechanisms for bone regeneration, specifically MSC osteogenic differentiation, proliferation and control of angiogenesis; therefore, it is a potential target for clinical bone regenerative therapies.

Cell therapy for cerebral hemorrhage: Five year follow-up report

The aim of the study was to examine treatment of cerebral hemorrhages with bone-marrow or human umbilical cord-derived mesenchymal stem cells (BMSCs or Hu-MSCs) and conventional surgical approaches, and determine and compare the effectiveness, feasibility, safety and reproducibility of each method. A retrospective analysis was performed on a cohort of cell-treated cerebral hemorrhage patients from October 1, 2007 to October 1, 2009. A total of 24 patients, all of whom received conventional surgical treatment, were classified as follows: i) The control group consisted of 8 patients who received only hematoma removal surgery, ii) the autologous group consisted of 7 patients who received additional autologous bone marrow mononuclear cell transplantation, and iii) the allograft group consisted of 9 patients who received additional umbilical cord mononuclear cell transplantation. After conventional hematoma removal surgery and X-ray supervision within 24 h and at 7 days, neurological disability and function tests were completed 3, 6, 12, 36 and 60 months later. The T-cell marker plasma levels were analyzed after 60 months. The results showed that, at approximately 3.5 months after graft the hematomas in all the groups were completely reabsorbed as observed on computed tomography scans. However, the functional outcomes in the cell-transplanted groups were better than in the control group after 5 years. While the National Institutes of Health Stroke Scale, modified Rankin score and modified Barthel index scores were simliar in the cell-transplanted groups, patients in the allograft group had better outcomes than those in the autologous graft group starting at 3 months and until the end of the follow-up period. The serum levels of T-cell markers CD4, CD56 and human leukocyte antigen-DR in the allograft group showed no signs of immunogenic graft complications and there were no significant differences in T-cell subtypes among the patient groups. The results of the present study suggest that, treatment of cerebral hemorrhage patients can be safely and effectively accomplished using Hu-MSC grafting and larger clinical trials should be considered in the future.

Secreted factors from adipose tissue-derived mesenchymal stem cells suppress oxygen/glucose deprivation-induced cardiomyocyte cell death via furin/PCSK-like enzyme activity

Clinical application of mesenchymal stem cells (MSCs) represents a potential novel therapy for currently intractable deteriorating diseases or traumatic injuries, including myocardial infarction. However, the molecular mechanisms of the therapeutic effects have not been precisely revealed. Herein, we report that conditioned media (CM) from rat adipose tissue-derived MSCs (ASCs) protected adult cardiomyocytes from oxygen/glucose deprivation (OGD)-induced cell death. We focused on furin/PCSK protease activity in ASC-CM because many therapeutic factors of MSCs and soluble cardioprotective factors include the PCSK cleavage site. We found that recombinant furin protected cardiomyocytes from OGD-induced cell death. The ASC-CM had potent furin/PCSK protease activity and the cardioprotective effect of the CM from ASCs in the OGD-assay was abolished by an inhibitor of the furin/PCSK-like enzyme. Microarray analysis and Western blot analysis showed PCSK5A, the secreted type of PCSK5, is the most abundantly secreted PCSK among 7 PCSK family members in ASC. Finally, knockdown of PCSK5A in ASCs decreased both the furin/PCSK protease activity and cardioprotective activity in the CM. These findings indicate an involvement of furin/PCSK-type protease(s) in the anti-ischemic activity of ASCs, and suggest a new mechanism of the therapeutic effect of MSCs.

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ASC-CM protects against OGD-induced cell death of adult cardiomyocytes.

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Furin/PCSK enzyme activity is protective against OGD-induced cell death.

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PCSK5A is the main component of cardioprotective activity of ASC-CM.

Macrophage phagocytosis alters the MRI signal of ferumoxytol-labeled mesenchymal stromal cells in cartilage defects

Human mesenchymal stem cells (hMSCs) are a promising tool for cartilage regeneration in arthritic joints. hMSC labeling with iron oxide nanoparticles enables non-invasive in vivo monitoring of transplanted cells in cartilage defects with MR imaging. Since graft failure leads to macrophage phagocytosis of apoptotic cells, we evaluated in vitro and in vivo whether nanoparticle-labeled hMSCs show distinct MR signal characteristics before and after phagocytosis by macrophages. We found that apoptotic nanoparticle-labeled hMSCs were phagocytosed by macrophages while viable nanoparticle-labeled hMSCs were not. Serial MRI scans of hMSC transplants in arthritic joints of recipient rats showed that the iron signal of apoptotic, nanoparticle-labeled hMSCs engulfed by macrophages disappeared faster compared to viable hMSCs. This corresponded to poor cartilage repair outcomes of the apoptotic hMSC transplants. Therefore, rapid decline of iron MRI signal at the transplant site can indicate cell death and predict incomplete defect repair weeks later. Currently, hMSC graft failure can be only diagnosed by lack of cartilage defect repair several months after cell transplantation. The described imaging signs can diagnose hMSC transplant failure more readily, which could enable timely re-interventions and avoid unnecessary follow up studies of lost transplants.

Short-term preconditioning enhances the therapeutic potential of adipose-derived stromal/stem cell-conditioned medium in cisplatin-induced acute kidney injury

The development of new strategies to preserve renal function after acute kidney injury (AKI) is necessary due to limited clinical intervention options. The organ-protective effects of mesenchymal stromal/stem cells (MSCs) and their conditioned medium (CM) have been investigated demonstrating that both separately promoted tubular recovery and ameliorated the outcome of AKI. Nevertheless, strategies to optimise the regenerative potential of both are highly needed. Here we investigated the effects of CM from adipose-derived MSCs (ASCs) preincubated in a hypoxic environment (Hyp). Protective factors were investigated by PCR analysis and a protein array in vitro. The expression of 64 of the 308 proteins assayed was found to be more than two-fold increased after Hyp. CM of Hyp-pretreated ASCs (pCM) was used to enhance regeneration in a mouse model of cisplatin-induced AKI (cisAKI). Renal function was assessed by measurements of markers for AKI and serum cytokine levels. The pCM significantly ameliorated serum creatinine and neutrophil gelatinase-associated lipocalin values, and also the levels of inflammatory cytokines IL-1β and IL-6 in the serum of mice with AKI. Our work clearly showed that a Hyp preconditioning significantly increases the release of protective factors in ASCs and enhances the therapeutic effects of CM in cisAKI in mice.

Argonaute and Argonaute-Bound Small RNAs in Stem Cells

Small RNAs are essential for a variety of cellular functions. Argonaute (AGO) proteins are associated with all of the different classes of small RNAs, and are indispensable in small RNA-mediated regulatory pathways. AGO proteins have been identified in various types of stem cells in diverse species from plants and animals. This review article highlights recent progress on how AGO proteins and AGO-bound small RNAs regulate the self-renewal and differentiation of distinct stem cell types, including pluripotent, germline, somatic, and cancer stem cells.

Characterization of human adipose tissue-derived stem cells with enhanced angiogenic and adipogenic properties

Autologous fat grafting is a popular method for soft tissue reconstructions but graft survival remains highly unpredictable. Supplementation of the graft with the stromal vascular fraction (SVF) or cultured adipose tissue-derived stem cells (ASCs) can enhance graft viability. In this study we have examined the phenotypic properties of a selected population of cells isolated from ASCs, with a view to determining their suitability for transplantation into grafts. ASCs were isolated from the SVF of human abdominal fat (n = 8 female patients) and CD146⁺ cells were selected using immunomagnetic beads. The angiogenic and adipogenic properties of the positively selected cells were compared with the negative fraction. CD146⁺ cells expressed the immunophenotypic characteristics of pericytes. With prolonged in vitro expansion, CD146^- cells exhibited increased population doubling times and morphological signs of senescence, whereas CD146⁺ cells did not. CD146⁺ cells expressed higher levels of the angiogenic molecules VEGF-A, angiopoietin-1 and FGF-1. Conditioned medium taken from CD146⁺ cells significantly increased formation of in vitro endothelial cell tube networks, whereas CD146^- cells did not. CD146⁺ cells could be differentiated into adipocytes in greater numbers than CD146^- cells. Consistent with this, differentiated CD146⁺ cells expressed higher levels of the adipocyte markers adiponectin and leptin. These results suggest that CD146⁺ cells selected from a heterogeneous mix of ASCs have more favourable angiogenic and adipogenic properties, which might provide significant benefits for reconstructive and tissue-engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.

Human Adipose-Derived Mesenchymal Stromal/Stem Cells Remain Viable and Metabolically Active Following Needle Passage

OBJECTIVE

To assess the biological effects of passage through clinically relevant needles on the viability and metabolic activity of culture-expanded, human adipose tissue-derived mesenchymal stromal/stem cells (AMSCs).

DESIGN

Prospective observational pilot study.

SETTING

Academic medical center.

PARTICIPANTS

Patient-derived clinical-grade culture expanded AMSCs.

INTERVENTIONS

AMSCs were passed through syringes without a needle attached (control), with an 18-gauge (25.4-mm) needle attached and with a 30-gauge (19-mm) needle attached at a constant injection flow rate and constant cell concentrations. Each injection condition was completed in triplicate.

MAIN OUTCOME MEASURES

Cell number and viability, proliferative capacity, metabolic activity, and acute gene expression as measured by cell counts, mitochondrial activity, and quantitative real time reverse-transcription polymerase chain reaction on day 0 (immediately), day 1, and day 4 after injection.

RESULTS

AMSC viability was not significantly affected by injection, and cells proliferated normally regardless of study group. Postinjection, AMSCs robustly expressed both proliferation markers and extracellular matrix proteins. Stress-response mRNAs were markedly but transiently increased independently of needle size within the first day in culture postinjection.

CONCLUSIONS

Human, culture-expanded AMSCs maintain their viability, proliferative capacity, and metabolic function following passage through needles as small as 30-gauge at constant flow rates of 4 mL/min, despite an early, nonspecific stress/cytoprotective response. These initial findings suggest that culture-expanded AMSCs should tolerate the injection process during most cell-based therapeutic interventions.

Adipose tissue-derived mesenchymal stem cells and platelet-rich plasma: stem cell transplantation methods that enhance stemness

Because of their ease of isolation and relative abundance, adipose-derived mesenchymal stem cells (ASCs) are a particularly attractive autologous cell source for various therapeutic purposes. ASCs retain a high proliferation capacity in vitro and have the ability to undergo extensive differentiation into multiple cell lineages. Moreover, ASCs secrete a wide range of growth factors that can stimulate tissue regeneration. Therefore, the clinical use of ASCs is feasible. However, the potential of ASCs differs depending on the donor's medical condition, including diseases such as diabetes. Recent studies demonstrated that ASCs from diabetic donors exhibit reduced proliferative potential and a smaller proportion of stem cell marker-positive cells. Therefore, to ensure the success of regenerative medicine, tissue engineering methods must be improved by the incorporation of factors that increase the proliferation and differentiation of stem/progenitor cells when autologous cells are used. Platelet-rich plasma (PRP), which contains high levels of diverse growth factors that can stimulate stem cell proliferation and cell differentiation in the context of tissue regeneration, has recently been identified as a biological material that could be applied to tissue regeneration. Thus, co-transplantation of ASCs and PRP represents a promising novel approach for cell therapy in regenerative medicine. In this review, we describe the potential benefits of adding PRP to ASCs and preclinical and clinical studies of this approach in various medical fields. We also discuss the mechanisms of PRP action and future cell-based therapies using co-transplantation of ASCs and PRP.

Potential of adipose-derived stem cells in muscular regenerative therapies

Regenerative capacity of skeletal muscles resides in satellite cells, a self-renewing population of muscle cells. Several studies are investigating epigenetic mechanisms that control myogenic proliferation and differentiation to find new approaches that could boost regeneration of endogenous myogenic progenitor populations. In recent years, a lot of effort has been applied to purify, expand and manipulate adult stem cells from muscle tissue. However, this population of endogenous myogenic progenitors in adults is limited and their access is difficult and invasive. Therefore, other sources of stem cells with potential to regenerate muscles need to be examined. An excellent candidate could be a population of adult stromal cells within fat characterized by mesenchymal properties, which have been termed adipose-derived stem cells (ASCs). These progenitor adult stem cells have been successfully differentiated in vitro to osteogenic, chondrogenic, neurogenic and myogenic lineages. Autologous ASCs are multipotent and can be harvested with low morbidity; thus, they hold promise for a range of therapeutic applications. This review will summarize the use of ASCs in muscle regenerative approaches.

Interleukin-17A-Induced Human Mesenchymal Stem Cells Are Superior Modulators of Immunological Function

Interferon-γ (IFN-γ)-preactivated mesenchymal stem cells (MSC-γ) are highly immunosuppressive but immunogenic in vivo due to their inherent expression of major histocompatibility (MHC) molecules. Here, we present an improved approach where we modified human bone marrow-derived MSC with interleukin-17A (MSC-17) to enhance T cell immunosuppression but not their immunogenicity. MSC-17, unlike MSC-γ, showed no induction or upregulation of MHC class I, MHC class II, and T cell costimulatory molecule CD40, but maintained normal MSC morphology and phenotypic marker expression. When cocultured with phytohemagglutinin (PHA)-activated human T cells, MSCs-17 were potent suppressors of T cell proliferation. Furthermore, MSC-17 inhibited surface CD25 expression and suppressed the elaboration of Th1 cytokines, IFN-γ, tumor necrosis factor-α (TNF-α), and IL-2 when compared with untreated MSCs (UT-MSCs). T cell suppression by MSC-17 correlated with increased IL-6 but not with indoleamine 2,3-dioxygenase 1, cyclooxygenase 1, and transforming growth factor β-1. MSC-17 but not MSC-γ consistently induced CD4(+) CD25(high) CD127(low) FoxP3(+) regulatory T cells (iTregs) from PHA-activated CD4(+) CD25(-) T cells. MSC-induced iTregs expressed CD39, CD73, CD69, OX40, cytotoxic T-lymphocyte associated antigen-4 (CTLA-4), and glucocorticoid-induced TNFR-related protein (GITR). These suppressive MSCs-17 can engender Tregs to potently suppress T cell activation with minimal immunogenicity and thus represent a superior T cell immunomodulator for clinical application.

MicroRNA Levels as Prognostic Markers for the Differentiation Potential of Human Mesenchymal Stromal Cell Donors

The ability of human mesenchymal stromal/stem cells (hMSCs) to differentiate into various mesenchymal cell lineages makes them a promising cell source for the use in tissue repair strategies. Since the differentiation potential of hMSCs differs between donors, it is necessary to establish biomarkers for the identification of donors with high differentiation potential. In this study, we show that microRNA (miRNA) expression levels are effective for distinguishing donors with high differentiation potential from low differentiation potential. Twenty hMSC donors were initially tested for marker expression and differentiation potential. In particular, the chondrogenic differentiation potential was evaluated on the basis of histological matrix formation, mRNA expression levels of chondrogenic marker genes, and quantitative glycosaminoglycan deposition. Three donors out of twenty were identified as donors with high chondrogenic potential, whereas nine showed moderate and eight showed low chondrogenic potential. Expression profiles of miRNAs involved in chondrogenesis and cartilage homeostasis were used for the distinction between high-performance hMSCs and low-performance hMSCs. Global mRNA expression profiles of the donors before the onset of chondrogenic differentiation revealed minor differences in gene expression between low and high chondrogenic performers. However, analysis of miRNA expression during a 7-day differentiation period identified miR-210 and miR-630 as positive regulators of chondrogenesis. In contrast, miR-181 and miR-34a, which are negative regulators of chondrogenesis, were upregulated during differentiation in low-performing donors. In conclusion, profiling of hMSC donors for a specific panel of miRNAs may have a prognostic value for selecting donors with high differentiation potential to improve hMSC-based strategies for tissue regeneration.

Human bone marrow stromal cell confluence: effects on cell characteristics and methods of assessment

BACKGROUND AIMS

Ex vivo expansion and serial passage of human bone marrow stromal cells (BMSCs, also known as bone marrow-derived mesenchymal stem cells) is required to obtain sufficient quantities for clinical therapy. The BMSC confluence criteria used to determine passage and harvest timing vary widely, and the impact of confluence on BMSC properties remains controversial. The effects of confluence on BMSC properties were studied and confluence-associated markers were identified.

METHODS

BMSC characteristics were analyzed as they grew from 50% to 100% confluence, including viability, population doubling time, apoptosis, colony formation, immunosuppression, surface marker expression, global gene expression and microRNA expression. In addition, culture supernatant protein, glucose, lactate and pH levels were analyzed.

RESULTS

Confluence-dependent changes were detected in the expression of several cell surface markers: 39 culture supernatant proteins, 26 microRNAs and 2078 genes. Many of these surface markers, proteins, microRNAs and genes have been reported to be important in BMSC function. The pigment epithelium-derived factor/vascular endothelial growth factor ratio increased with confluence, but 80% and 100% confluent BMSCs demonstrated a similar level of immunosuppression of mixed lymphocyte reactions. In addition, changes in lactate and glucose levels correlated with BMSC density.

CONCLUSIONS

BMSC characteristics change as confluence increases. 100% confluent BMSCs may have compromised pro-angiogenesis properties but may retain their immunomodulatory properties. Supernatant lactate and glucose levels can be used to estimate confluence and ensure consistency in passage and harvest timing. Flow cytometry or microRNA expression can be used to confirm that the BMSCs have been harvested at the appropriate confluence.

MSCs seeded on bioengineered scaffolds improve skin wound healing in rats

Growing evidence has shown the promise of mesenchymal stromal cells (MSCs) for the treatment of cutaneous wound healing. We have previously demonstrated that MSCs seeded on an artificial dermal matrix, Integra (Integra Lifesciences Corp., Plainsboro, NJ) enriched with platelet-rich plasma (Ematrix) have enhanced proliferative potential in vitro as compared with those cultured on the scaffold alone. In this study, we extended the experimentation by evaluating the efficacy of the MSCs seeded scaffolds in the healing of skin wounds in an animal model in vivo. It was found that the presence of MSCs within the scaffolds greatly ameliorated the quality of regenerated skin, reduced collagen deposition, enhanced reepithelization, increased neo-angiogenesis, and promoted a greater return of hair follicles and sebaceous glands. The mechanisms involved in these beneficial effects were likely related to the ability of MSCs to release paracrine factors modulating the wound healing response. MSC-seeded scaffolds, in fact, up-regulated matrix metalloproteinase 9 expression in the extracellular matrix and enhanced the recruitment of endogenous progenitors during tissue repair. In conclusion, the results of this study provide evidence that the treatment with MSC-seeded scaffolds of cutaneous wounds contributes to the recreation of a suitable microenvironment for promoting tissue repair/regeneration at the implantation sites.

Cell senescence abrogates the therapeutic potential of human mesenchymal stem cells in the lethal endotoxemia model

Mesenchymal stem cells (MSCs) possess unique paracrine and immunosuppressive properties, which make them useful candidates for cellular therapy. Here, we address how cellular senescence influences the therapeutic potential of human MSCs (hMSCs). Senescence was induced in bone marrow-derived hMSC cultures with gamma irradiation. Control and senescent cells were tested for their immunoregulatory activity in vitro and in vivo, and an extensive molecular characterization of the phenotypic changes induced by senescence was performed. We also compared the gene expression profiles of senescent hMSCs with a collection of hMSCs used in an ongoing clinical study of Graft Versus Host disease (GVHD). Our results show that senescence induces extensive phenotypic changes in hMSCs and abrogates their protective activity in a murine model of LPS-induced lethal endotoxemia. Although senescent hMSCs retain an ability to regulate the inflammatory response on macrophages in vitro, and, in part retain their capacity to significantly inhibit lymphocyte proliferation, they have a severely impaired migratory capacity in response to proinflammatory signals, which is associated with an inhibition of the AP-1 pathway. Additionally, expression analysis identified PLEC, C8orf48, TRPC4, and ZNF14, as differentially regulated genes in senescent hMSCs that were similarly regulated in those hMSCs which failed to produce a therapeutic effect in a GVHD trial. All the observed phenotypic alterations were confirmed in replicative-senescent hMSCs. In conclusion, this study highlights important changes in the immunomodulatory phenotype of senescent hMSCs and provides candidate gene signatures which may be useful to evaluate the therapeutic potential of hMSCs used in future clinical studies.

Interferon-gamma modification of mesenchymal stem cells: implications of autologous and allogeneic mesenchymal stem cell therapy in allotransplantation

Bone marrow-derived mesenchymal stem cells (MSC) have unique immunomodulatory and reparative properties beneficial for allotransplantation cellular therapy. The clinical administration of autologous or allogeneic MSC with immunosuppressive drugs is able to prevent and treat allograft rejection in kidney transplant recipients, thus supporting the immunomodulatory role of MSC. Interferon-gamma (IFN-γ) is known to enhance the immunosuppressive properties of MSC. IFN-γ preactivated MSC (MSC-γ) directly or indirectly modulates T cell responses by enhancing or inducing MSC inhibitory factors. These factors are known to downregulate T cell activation, enhance T cell negative signalling, alter T cells from a proinflammatory to an anti-inflammatory phenotype, interact with antigen-presenting cells and increase or induce regulatory cells. Highly immunosuppressive MSC-γ with increased migratory and reparative capacities may aid tissue repair, prolong allograft survival and induce allotransplant tolerance in experimental models. Nevertheless, there are contradictory in vivo observations related to allogeneic MSC-γ therapy. Many studies report that allogeneic MSC are immunogenic due to their inherent expression of major histocompatibility (MHC) molecules. Enhanced expression of MHC in allogeneic MSC-γ may increase their immunogenicity and this can negatively impact allograft survival. Therefore, strategies to reduce MSC-γ immunogenicity would facilitate "off-the-shelf" MSC therapy to efficiently inhibit alloimmune rejection and promote tissue repair in allotransplantation. In this review, we examine the potential benefits of MSC therapy in the context of allotransplantation. We also discuss the use of autologous and allogeneic MSC and the issues associated with their immunogenicity in vivo, with particular focus on the use of enhanced MSC-γ cellular therapy.

Application of stems cells in wound healing--an update

Wound healing is a complex but well-orchestrated tissue repair process composed of a series of molecular and cellular events conducted by various types of cells and extracellular matrix. Despite a variety of therapeutic strategies proposed to accelerate the healing of acute and/or chronic wounds over the past few decades, effective treatment of chronic nonhealing wounds still remains a challenge. Due to the recent advances in stem cell research, a dramatic enthusiasm has been drawn to the application of stem cells in regenerative medicine. Both embryonic and adult stem cells have prolonged self-renewal capacity and are able to differentiate into various tissue types. Nevertheless, use of embryonic stem cells is limited, owing to ethical concerns and legal restrictions. Adult stem cells, which could be isolated from bone marrow, umbilical cord blood, adipose tissue, skin and hair follicles,are being explored extensively to facilitate the healing of both acute and chronic wounds. The current article summarizes recent research on various types of stem cell-based strategies applied to improve wound healing. In addition, future directions of stem cell-based therapy in wound healing have also been discussed. Finally, despite its apparent advantages, limitations and challenges of stem cell therapy are discussed.

miR-21 in ischemia/reperfusion injury: a double-edged sword?

MicroRNAs (miRNAs or miRs) are endogenous, small RNA molecules that suppress expression of targeted mRNA. miR-21, one of the most extensively studied miRNAs, is importantly involved in divergent pathophysiological processes relating to ischemia/reperfusion (I/R) injury, such as inflammation and angiogenesis. The role of miR-21 in renal I/R is complex, with both protective and pathological pathways being regulated by miR-21. Preconditioning-induced upregulation of miR-21 contributes to the protection against subsequent renal I/R injury through the targeting of genes such as the proapoptotic gene programmed cell death 4 and interactions between miR-21 and hypoxia-inducible factor. Conversely, long-term elevation of miR-21 may be detrimental to the organ by promoting the development of renal interstitial fibrosis following I/R injury. miR-21 is importantly involved in several pathophysiological processes related to I/R injury including inflammation and angiogenesis as well as the biology of stem cells that could be used to treat I/R injury; however, the effect of miR-21 on these processes in renal I/R injury remains to be studied.

Adipose-derived mesenchymal stromal/stem cells: An update on their phenotype in vivo and in vitro

Adipose tissue is a rich, ubiquitous and easily accessible source for multipotent stromal/stem cells and has, therefore, several advantages compared to other sources of mesenchymal stromal/stem cells. Several studies have tried to identify the origin of the stromal/stem cell population within adipose tissue in situ. This is a complicated attempt because no marker has currently been described which unambiguously identifies native adipose-derived stromal/stem cells (ASCs). Isolated and cultured ASCs are a non-uniform preparation consisting of several subsets of stem and precursor cells. Cultured ASCs are characterized by their expression of a panel of markers (and the absence of others), whereas their in vitro phenotype is dynamic. Some markers were expressed de novo during culture, the expression of some markers is lost. For a long time, CD34 expression was solely used to characterize haematopoietic stem and progenitor cells, but now it has become evident that it is also a potential marker to identify an ASC subpopulation in situ and after a short culture time. Nevertheless, long-term cultured ASCs do not express CD34, perhaps due to the artificial environment. This review gives an update of the recently published data on the origin and phenotype of ASCs both in vivo and in vitro. In addition, the composition of ASCs (or their subpopulations) seems to vary between different laboratories and preparations. This heterogeneity of ASC preparations may result from different reasons. One of the main problems in comparing results from different laboratories is the lack of a standardized isolation and culture protocol for ASCs. Since many aspects of ASCs, such as the differential potential or the current use in clinical trials, are fully described in other recent reviews, this review further updates the more basic research issues concerning ASCs’ subpopulations, heterogeneity and culture standardization.

Stem cell-based therapies for ischemic stroke

In recent years, stem cell-based approaches have attracted more attention from scientists and clinicians due to their possible therapeutical effect on stroke. Animal studies have demonstrated that the beneficial effects of stem cells including embryonic stem cells (ESCs), inducible pluripotent stem cells (iPSCs), neural stem cells (NSCs), and mesenchymal stem cell (MSCs) might be due to cell replacement, neuroprotection, endogenous neurogenesis, angiogenesis, and modulation on inflammation and immune response. Although several clinical studies have shown the high efficiency and safety of stem cell in stroke management, mainly MSCs, some issues regarding to cell homing, survival, tracking, safety, and optimal cell transplantation protocol, such as cell dose and time window, should be addressed. Undoubtably, stem cell-based gene therapy represents a novel potential therapeutic strategy for stroke in future.

Analysis of the transfer of circulating microRNA between cells mediated by gap junction

A significant breakthrough in the field of research was the identification of microRNAs (miRNAs), which are small molecule, single-stranded nucleic acids. MiRNAs have diverse roles in cellular biology with the ability for translation in different areas of medicine. The size of miRNAs provides them for passage through gap junction. Recent studies have demonstrated the passage of miRNAs through gap junctional intercellular communication (GJIC) among cancer cells and between breast cancer cells and bone marrow stroma. The transfer of miRNAs has been implicated in the etiology of breast cancer dormancy. To this end, we have developed a miRNA reporter assay to assess the ability of miRNAs to be transferred between stem and breast cancer cells and target a specific recognition sequence.

Label retention identifies a multipotent mesenchymal stem cell-like population in the postnatal thymus

Thymic microenvironments are essential for the proper development and selection of T cells critical for a functional and self-tolerant adaptive immune response. While significant turnover occurs, it is unclear whether populations of adult stem cells contribute to the maintenance of postnatal thymic epithelial microenvironments. Here, the slow cycling characteristic of stem cells and their property of label-retention were used to identify a K5-expressing thymic stromal cell population capable of generating clonal cell lines that retain the capacity to differentiate into a number of mesenchymal lineages including adipocytes, chondrocytes and osteoblasts suggesting a mesenchymal stem cell-like phenotype. Using cell surface analysis both culture expanded LRCs and clonal thymic mesenchymal cell lines were found to express Sca1, PDGFRα, PDGFRβ,CD29, CD44, CD49F, and CD90 similar to MSCs. Sorted GFP-expressing stroma, that give rise to TMSC lines, contribute to thymic architecture when reaggregated with fetal stroma and transplanted under the kidney capsule of nude mice. Together these results show that the postnatal thymus contains a population of mesenchymal stem cells that can be maintained in culture and suggests they may contribute to the maintenance of functional thymic microenvironments.

New approach of bone marrow-derived mesenchymal stem cells and human amniotic epithelial cells applications in accelerating wound healing of irradiated albino rats

BACKGROUND AND OBJECTIVES

Irradiated wound healing is a highly complex and dynamic process. The latest technology making a huge difference in this process is stem cell therapy. The goal of this study was to evaluate the use of bone marrow-derived mesenchymal stem cells (BM-MSCs) or human amniotic epithelial cells (HAECs) in the healing of irradiated wounds.

METHODS AND RESULTS

Forty five male albino rats were subjected to whole body 6 gray gamma radiations. One day post irradiation, full-thickness incisional wound was created in the tibial skin. The rats were randomly equally divided into three groups. The incisions of the first group (gp I) were injected intra-dermally with saline before stitching and those of both the second (gp II) and the third groups (gp III) were intradermally injected with BM-MSCs and HAECs before stitching respectively. Animals were sacrificed after the third, seventh and fourteenth days postoperative. The healing process was assessed histopathologically. CXCL-5, SDF-1 and Transforming growth factor-beta 1 (TGF-β1) expression were also detected in biopsies from all wounds. Expression of TGF-β1 in gp I was more than the other groups leading to severe inflammation, deficient healed dermis and delayed reepithelialization. SDF-1 expression was high in gp II while CXCL-5 expression was high in gp III causing accelerated wound healing. BM-MSCs showed a great effect on the quality of the dermis, while superiority of the epithelium and its appendages were achieved in HAECs group.

CONCLUSIONS

Using BM-MSCs and HAECs could be used safely in case of irradiated wounds.

COMP-Ang1 promotes chondrogenic and osteogenic differentiation of multipotent mesenchymal stem cells through the Ang1/Tie2 signaling pathway

Mesenchymal stem cells (MSCs) are pleiotrophic cells that differentiate to chondrocytes, osteoblasts, or adipocytes, as a result of crosstalk by specific signaling pathways including MAPK pathway. Recently cartilage oligomeric matrix protein angiopoietin1 (COMP-Ang1), an Ang1 variant which is more potent than native Ang1 in phosphorylating Tie2 receptor was developed. The Ang1/Tie2 signaling system not only plays a pivotal role in vessel growth, remodeling, and maturation, but also protective and recruit effect on MSCs. Thus, the aim of the present study was to investigate the differentiate effect of Ang1/Tie2 signaling on MSCs in the presence of chondrogenic, osteogenic and adipogenic induction medium, and to determine the possible mechanisms. Our results clearly demonstrated that MSCs cultured in each induction medium with COMP-Ang1 revealed strongly chondrogenic and osteogenic morphological change (3.5- and 2-fold, respectively) as well as up-regulate each gene, except for adipogenic differentiation. Accordingly, we found that phosphorylation of Tie2 expression lead to phosphorylation of p38 and AKT and then accelerating each differentiation of MSCs to chondrocytes and osteoblasts. Therefore, our findings suggest that COMP-Ang1 present a portal to promote MSCs differentiation to chondrocytes and osteoblasts through Ang1/Tie2 signaling pathway and provide insights into novel therapies for bone diseases.

Gingiva as a source of stem cells with therapeutic potential

Postnatal connective tissues contain phenotypically heterogeneous cells populations that include distinct fibroblast subpopulations, pericytes, myofibroblasts, fibrocytes, and tissue-specific mesenchymal stem cells (MSCs). These cells play key roles in tissue development, maintenance, and repair and contribute to various pathologies. Depending on the origin of tissue, connective tissue cells, including MSCs, have different phenotypes. Understanding the identity and specific functions of these distinct tissue-specific cell populations may allow researchers to develop better treatment modalities for tissue regeneration and find novel approaches to prevent pathological conditions. Interestingly, MSCs from adult oral mucosal gingiva possess distinct characteristics, including neural crest origin, multipotent differentiation capacity, fetal-like phenotype, and potent immunomodulatory properties. These characteristics and an easy, relatively noninvasive access to gingival tissue, and fast tissue regeneration after tissue biopsy make gingiva an attractive target for cell isolation for therapeutic purposes aiming to promote tissue regeneration and fast, scar-free wound healing. The purpose of this review is to discuss the identity, phenotypical heterogeneity, and function of gingival MSCs and summarize what is currently known about their properties, role in scar-free healing, and their future therapeutic potential.

COMP-Ang1 inhibits apoptosis as well as improves the attenuated osteogenic differentiation of mesenchymal stem cells induced by advanced glycation end products

BACKGROUND

In the present study, we have investigated the possibility that cartilage oligomeric matrix protein angiopoietin1 (COMP-Ang1), important factor in angiogenesis, osteogenesis and the survival of mesenchymal stem cells (MSCs) through the Ang1/Tie2 pathway has beneficial effects on osteogenic differentiated cells (ODCs) from MSCs treated by advanced glycation end products (AGE), which are pathological factors of diabetes.

METHODS

Primary culture of MSCs was used. For comparison analysis of AGE and COMP-Ang1 effects, we performed cell viability assay with each treated variety concentration for 24h. Apoptosis rate and Caspase-3 activity were measured by each ELISA assay. To make sure with Ang1/Tie2 pathway, we performed small interfering RNA transfected to MSCs. Real-time RT-PCR was performed to identify ODCs marker genes. Immunoblotting was used to evaluate the expression of Tie2, AKT, p38 and ERK.

RESULTS

Our results clearly demonstrate that COMP-Ang1 upregulates the phosphorylation of AKT and p38 by activating the Ang1/Tie2 signaling pathway, indicating that COMP-Ang1 affects both AGE-induced apoptosis and the attenuated osteogenic differentiation of MSCs through the p38/MAPK and PI3K/AKT pathways.

CONCLUSIONS

COMP-Ang1 improves cell viability and differentiation function of ODCs against AGE via Ang/Tie2 signaling pathway.

GENERAL SIGNIFICANCE

Our results suggest the potential importance of COMP-Ang1 as a new therapy for impaired bone formation that is associated with diabetes and advanced age.

Bone regeneration by transplantation of human mesenchymal stromal cells in a rabbit mandibular distraction osteogenesis model

Ex vivo expanded mesenchymal stromal cells (MSCs) represent a potential cell population for tissue regeneration strategy. Xenogeneic transplantation using human MSCs (hMSCs) can be an approach to reveal what hMSCs guide in bone regeneration with distinguishable gene expression from a host animal. In this study, we investigated the regenerating effect of hMSCs varying injection time point in a rabbit distraction osteogenesis model. Undifferentiated hMSCs (2×10(6) cells) were injected transcutaneously into the osteotomy site of one side of the mandible 1 day before the onset of distraction (Group 1) or after distraction (Group 2). The contralateral side of the mandible, which was subjected to distraction, but no hMSC injection, was used as the control in each group. hMSCs showed lack of major histocompatibility complex class II expression and suppression of xenogeneic lymphocyte proliferation stimulated by a proinflammatory cytokine. A microcomputed tomography-based evaluation showed a significant increase in new bone volume in the distracted callus in Group 1 compared to the contralateral side. Injection of hMSCs increased the bone mineral density (BMD) of the regenerated bone in both Group 1 and 2, although the former had a higher BMD than the latter. hMSCs of Group 1 subjected to distraction after injection expressed insulin-like growth factor-1 (IGF-1) and fibronectin (FN), while the expression of most osteoblast differentiation-related markers and growth factors was negligible. These results demonstrated that hMSCs exerted immune suppressive behavior in rabbit T cells in vitro, and hMSC transplantation into the distracted callus of a rabbit model provided osteogenic benefits that were more pronounced when the hMSCs were injected just before distraction than at the end of distraction. The beneficial effect of hMSCs might be mediated, partly by the expression of matrix proteins or IGF-1, which are known to favor bone formation.

An update review of stem cell applications in burns and wound care

The ultimate goal of the treatment of cutaneous burns and wounds is to restore the damaged skin both structurally and functionally to its original state. Recent research advances have shown the great potential of stem cells in improving the rate and quality of wound healing and regenerating the skin and its appendages. Stem cell-based therapeutic strategies offer new prospects in the medical technology for burns and wounds care. This review seeks to give an updated overview of the applications of stem cell therapy in burns and wound management since our previous review of the “stem cell strategies in burns care”.

Progress in stem cell therapy for the diabetic foot

The diabetic foot is a common and severe complication of diabetes comprising a group of lesions including vasculopathy, neuropathy, tissue damage and infection. Vasculopathy due to ischemia is a major contributor to the pathogenesis, natural history and outcome of the diabetic foot. Despite conventional revascularization interventions including angioplasty, stenting, atherectomy and bypass grafts to vessels, a high incidence of amputation persists. The need to develop alternative therapeutic options is compelling; stem cell therapy aims to increase revascularization and alleviate limb ischemia or improve wound healing by stimulating new blood vessel formation, and brings new hope for the treatment of the diabetic foot.

Mechanisms of action of mesenchymal stem cells in cutaneous wound repair and regeneration

Mesenchymal stem cells (MSCs) are multipotent cells with the capacity for self-renewal and differentiation and have a broad tissue distribution. These characteristics make them candidate cells for wound healing and regeneration in a variety of disorders. Endogenous MSCs or exogenously delivered MSCs can traffic and migrate to injured tissue and participate in the healing of this tissue. The concentrated conditioned medium from MSCs can modulate wound repair without MSCs being present in the wound. The therapeutic effects of MSCs might be attributable to their ability to differentiate and transdifferentiate into tissue-specific cells, to fuse with the resident cells, to secrete a wide array of paracrine factors in order to stimulate the survival and functional recovery of the resident cells, or to regulate the local microenviroment or niche and immune response. These mechanisms are probably independent but not mutually exclusive. In many circumstances, a combination of these protective mechanisms might work together to affect cutaneous wound healing. This review gives a brief overview and discusses the mechanisms by which MSCs promote skin repair and regeneration, although the specific mechanisms in each type of cutaneous wound are still unclear and controversial. A comprehensive understanding of the mechanisms should allow us to find advanced and better treatment strategies for various skin diseases, even those that are currently incurable.

Adipose-derived mesenchymal stromal/stem cells: tissue localization, characterization, and heterogeneity

Adipose tissue as a stem cell source is ubiquitously available and has several advantages compared to other sources. It is easily accessible in large quantities with minimal invasive harvesting procedure, and isolation of adipose-derived mesenchymal stromal/stem cells (ASCs) yields a high amount of stem cells, which is essential for stem-cell-based therapies and tissue engineering. Several studies have provided evidence that ASCs in situ reside in a perivascular niche, whereas the exact localization of ASCs in native adipose tissue is still under debate. ASCs are isolated by their capacity to adhere to plastic. Nevertheless, recent isolation and culture techniques lack standardization. Cultured cells are characterized by their expression of characteristic markers and their capacity to differentiate into cells from meso-, ecto-, and entodermal lineages. ASCs possess a high plasticity and differentiate into various cell types, including adipocytes, osteoblasts, chondrocytes, myocytes, hepatocytes, neural cells, and endothelial and epithelial cells. Nevertheless, recent studies suggest that ASCs are a heterogeneous mixture of cells containing subpopulations of stem and more committed progenitor cells. This paper summarizes and discusses the current knowledge of the tissue localization of ASCs in situ, their characterization and heterogeneity in vitro, and the lack of standardization in isolation and culture methods.

Cyclic ADP ribose is a novel regulator of intracellular Ca2+ oscillations in human bone marrow mesenchymal stem cells

Bone marrow mesenchymal stem cells (MSCs) are a promising cell source for regenerative medicine. However, the cellular biology of these cells is not fully understood. The present study characterizes the cyclic ADP-ribose (cADPR)-mediated Ca(2+) signals in human MSCs and finds that externally applied cADPR can increase the frequency of spontaneous intracellular Ca(2+) (Ca(2+) (i) ) oscillations. The increase was abrogated by a specific cADPR antagonist or an inositol trisphosphate receptor (IP3R) inhibitor, but not by ryanodine. In addition, the cADPR-induced increase of Ca(2+) (i) oscillation frequency was prevented by inhibitors of nucleoside transporter or by inhibitors of the transient receptor potential cation melastatin-2 (TRPM2) channel. RT-PCR revealed mRNAs for the nucleoside transporters, concentrative nucleoside transporters 1/2 and equilibrative nucleoside transporters 1/3, IP3R1/2/3 and the TRPM2 channel, but not those for ryanodine receptors and CD38 in human MSCs. Knockdown of the TRPM2 channel by specific short interference RNA abolished the effect of cADPR on the Ca(2+) (i) oscillation frequency, and prevented the stimulation of proliferation by cADPR. Moreover, cADPR remarkably increased phosphorylated extracellular-signal-regulated kinases 1/2 (ERK1/2), but not Akt or p38 mitogen-activated protein kinase (MAPK). However, cADPR had no effect on adipogenesis or osteogenesis in human MSCs. Our results indicate that cADPR is a novel regulator of Ca(2+) (i) oscillations in human MSCs. It permeates the cell membrane through the nucleoside transporters and increases Ca(2+) oscillation via activation of the TRPM2 channel, resulting in enhanced phosphorylation of ERK1/2 and, thereby, stimulation of human MSC proliferation. This study delineates an alternate signalling pathway of cADPR that is distinct from its well-established role of serving as a Ca(2+) messenger for mobilizing the internal Ca(2+) stores. Whether cADPR can be used clinically for stimulating marrow function in patients with marrow disorders remains to be further studied.

Bone marrow and adipose stem cells can be tracked with PKH26 until post staining passage 6 in in vitro and in vivo

Tracking of transplanted cells has become an important procedure in cell therapy. We studied the in vitro dye retention, survival and in vivo tracking of stem cells with PKH26 dye. Sheep BMSCs and ADSCs were labeled with 2, 4 and 8 μmol of PKH26 and monitored for six passages. Labeled BMSCs and ADSCs acquired mean cumulative population doubling of 12.7±0.4 and 14.6±0.5; unlabeled samples had 13.8±0.5 and 15.4±0.6 respectively. Upon staining with 2, 4 and 8 μmol PKH26, BMSCs had retentions of 40.0±5.8, 60.0±2.9 and 95.0±2.9%, while ADSCs had 92.0±1.2, 95.0±1.2 and 98.0±1.2%. ADSCs retentions were significantly higher at 2 and 4 μmol. On dye retention comparison at 8 μmol and 4 μmol for BMSCs and ADSCs; ADSCs were significantly higher at passages 2 and 3. The viability of BMSCs reduced from 94.0±1.2% to 90.0±0.6% and ADSCs from 94.0±1.2% to 52.0±1.2% (p<0.05) after 24h. BMSCs had significant up regulation of the cartilage genes for both the labeled and the unlabeled samples compared to ADSCs (p<0.05). PKH26 fluorescence was detected on the resected portions of the regenerated neo-cartilage. The recommended concentration of PKH26 for ADSCs is 2 μmol and BMSCs is 8 μmol, and they can be tracked up to 49 days.

Stimulation of skin and wound fibroblast migration by mesenchymal stem cells derived from normal donors and chronic wound patients

Chronic wounds continue to be a major cause of morbidity for patients and an economic burden on the health care system. Novel therapeutic approaches to improved wound healing will need, however, to address cellular changes induced by a number of systemic comorbidities seen in chronic wound patients, such as diabetes, chronic renal failure, and arterial or venous insufficiency. These effects likely include impaired inflammatory cell migration, reduced growth factor production, and poor tissue remodeling. The multifunctional properties of bone marrow-derived mesenchymal stem cells (MSCs), including their ability to differentiate into various cell types and capacity to secrete factors important in accelerating healing of cutaneous wounds, have made MSCs a promising agent for tissue repair and regeneration. In this study we have used an in vitro scratch assay procedure incorporating labeled MSCs and fibroblasts derived from normal donors and chronic wound patients in order to characterize the induction of mobilization when these cells are mixed. A modified Boyden chamber assay was also used to examine the effect of soluble factors on fibroblast migration. These studies suggest that MSCs play a role in skin wound closure by affecting dermal fibroblast migration in a dose-dependent manner. Deficiencies were noted, however, in chronic wound patient fibroblasts and MSCs as compared with those derived from normal donors. These findings provide a foundation to develop therapies targeted specifically to the use of bone marrow-derived MSCs in wound healing and may provide insight into why some wounds do not heal.